Re: performance trouble

[Vadim Rozenfeld <vrozenfe@redhat.com>]

On Tuesday, March 27, 2012 05:58:01 PM Peter Lieven wrote:
> On 27.03.2012 17:44, Vadim Rozenfeld wrote:
> > On Tuesday, March 27, 2012 04:06:13 PM Peter Lieven wrote:
> >> On 27.03.2012 14:29, Gleb Natapov wrote:
> >>> On Tue, Mar 27, 2012 at 02:28:04PM +0200, Peter Lieven wrote:
> >>>> On 27.03.2012 14:26, Gleb Natapov wrote:
> >>>>> On Tue, Mar 27, 2012 at 02:20:23PM +0200, Peter Lieven wrote:
> >>>>>> On 27.03.2012 12:00, Gleb Natapov wrote:
> >>>>>>> On Tue, Mar 27, 2012 at 11:26:29AM +0200, Peter Lieven wrote:
> >>>>>>>> On 27.03.2012 11:23, Vadim Rozenfeld wrote:
> >>>>>>>>> On Tuesday, March 27, 2012 10:56:05 AM Gleb Natapov wrote:
> >>>>>>>>>> On Mon, Mar 26, 2012 at 10:11:43PM +0200, Vadim Rozenfeld wrote:
> >>>>>>>>>>> On Monday, March 26, 2012 08:54:50 PM Peter Lieven wrote:
> >>>>>>>>>>>> On 26.03.2012 20:36, Vadim Rozenfeld wrote:
> >>>>>>>>>>>>> On Monday, March 26, 2012 07:52:49 PM Gleb Natapov wrote:
> >>>>>>>>>>>>>> On Mon, Mar 26, 2012 at 07:46:03PM +0200, Vadim Rozenfeld
> > 
> > wrote:
> >>>>>>>>>>>>>>> On Monday, March 26, 2012 07:00:32 PM Peter Lieven wrote:
> >>>>>>>>>>>>>>>> On 22.03.2012 10:38, Vadim Rozenfeld wrote:
> >>>>>>>>>>>>>>>>> On Thursday, March 22, 2012 10:52:42 AM Peter Lieven 
wrote:
> >>>>>>>>>>>>>>>>>> On 22.03.2012 09:48, Vadim Rozenfeld wrote:
> >>>>>>>>>>>>>>>>>>> On Thursday, March 22, 2012 09:53:45 AM Gleb Natapov
> > 
> > wrote:
> >>>>>>>>>>>>>>>>>>>> On Wed, Mar 21, 2012 at 06:31:02PM +0100, Peter Lieven
> > 
> > wrote:
> >>>>>>>>>>>>>>>>>>>>> On 21.03.2012 12:10, David Cure wrote:
> >>>>>>>>>>>>>>>>>>>>>> 		hello,
> >>>>>>>>>>>>>>>>>>>>>> 
> >>>>>>>>>>>>>>>>>>>>>> Le Tue, Mar 20, 2012 at 02:38:22PM +0200, Gleb
> >>>>>>>>>>>>>>>>>>>>>> Natapov
> >>>>>>>>> 
> >>>>>>>>> ecrivait :
> >>>>>>>>>>>>>>>>>>>>>>> Try to add<feature policy='disable'
> >>>>>>>>>>>>>>>>>>>>>>> name='hypervisor'/>  to cpu definition in XML and
> >>>>>>>>>>>>>>>>>>>>>>> check command line.
> >>>>>>>>>>>>>>>>>>>>>>> 
> >>>>>>>>>>>>>>>>>>>>>> 	ok I try this but I can't use<cpu model>         
> >>>>>>>>>>>>>>>>>>>>>> 	to map the host cpu
> >>>>>>>>>>>>>>>>>>>>>> 
> >>>>>>>>>>>>>>>>>>>>>> (my libvirt is 0.9.8) so I use :
> >>>>>>>>>>>>>>>>>>>>>>        <cpu match='exact'>
> >>>>>>>>>>>>>>>>>>>>>>        
> >>>>>>>>>>>>>>>>>>>>>>          <model>Opteron_G3</model>
> >>>>>>>>>>>>>>>>>>>>>>          <feature policy='disable'
> >>>>>>>>>>>>>>>>>>>>>>          name='hypervisor'/>
> >>>>>>>>>>>>>>>>>>>>>>        
> >>>>>>>>>>>>>>>>>>>>>>        </cpu>
> >>>>>>>>>>>>>>>>>>>>>> 	
> >>>>>>>>>>>>>>>>>>>>>> 	(the physical server use Opteron CPU).
> >>>>>>>>>>>>>>>>>>>>>> 
> >>>>>>>>>>>>>>>>>>>>>> 	The log is here :
> >>>>>>>>>>>>>>>>>>>>>> http://www.roullier.net/Report/report-3.2-vhost-net-
> >>>>>>>>>>>>>>>>>>>>>> 1v cpu-cp u.tx t.gz
> >>>>>>>>>>>>>>>>>>>>>> 
> >>>>>>>>>>>>>>>>>>>>>> 	And now with only 1 vcpu, the response time is
> >>>>>>>>>>>>>>>>>>>>>> 	8.5s, great
> >>>>>>>>>>>>>>>>>>>>>> 
> >>>>>>>>>>>>>>>>>>>>>> improvment. We keep this configuration for
> >>>>>>>>>>>>>>>>>>>>>> production
> >>>>>>>>>>>>>>>>>>>>>> 
> >>>>>>>>>>>>>>>>>>>>>> : we check the response time when some other users
> >>>>>>>>>>>>>>>>>>>>>> 
> >>>>>>>>>>>>>>>>>>>>>> are connected.
> >>>>>>>>>>>>>>>>>>>>> 
> >>>>>>>>>>>>>>>>>>>>> please keep in mind, that setting -hypervisor,
> >>>>>>>>>>>>>>>>>>>>> disabling hpet and only one vcpu
> >>>>>>>>>>>>>>>>>>>>> makes windows use tsc as clocksource. you have to
> >>>>>>>>>>>>>>>>>>>>> make sure, that your vm is not switching between
> >>>>>>>>>>>>>>>>>>>>> physical sockets on your system and that you have
> >>>>>>>>>>>>>>>>>>>>> constant_tsc feature to have a stable tsc between
> >>>>>>>>>>>>>>>>>>>>> the cores in the same socket. its also likely that
> >>>>>>>>>>>>>>>>>>>>> the vm will crash when live migrated.
> >>>>>>>>>>>>>>>>>>>> 
> >>>>>>>>>>>>>>>>>>>> All true. I asked to try -hypervisor only to verify
> >>>>>>>>>>>>>>>>>>>> where we loose performance. Since you get good result
> >>>>>>>>>>>>>>>>>>>> with it frequent access to PM timer is probably the
> >>>>>>>>>>>>>>>>>>>> reason. I do not recommend using -hypervisor for
> >>>>>>>>>>>>>>>>>>>> production!
> >>>>>>>>>>>>>>>>>>>> 
> >>>>>>>>>>>>>>>>>>>>> @gleb: do you know whats the state of in-kernel
> >>>>>>>>>>>>>>>>>>>>> hyper-v timers?
> >>>>>>>>>>>>>>>>>>>> 
> >>>>>>>>>>>>>>>>>>>> Vadim is working on it. I'll let him answer.
> >>>>>>>>>>>>>>>>>>> 
> >>>>>>>>>>>>>>>>>>> It would be nice to have synthetic timers supported.
> >>>>>>>>>>>>>>>>>>> But,
> >>>>>>>>>>>>>>>>>>> 
> >>>>>>>>>>>>>>>>>>>   at the moment, I'm only researching  this feature.
> >>>>>>>>>>>>>>>>>> 
> >>>>>>>>>>>>>>>>>> So it will take months at least?
> >>>>>>>>>>>>>>>>> 
> >>>>>>>>>>>>>>>>> I would say weeks.
> >>>>>>>>>>>>>>>> 
> >>>>>>>>>>>>>>>> Is there a way, we could contribute and help you with
> >>>>>>>>>>>>>>>> this?
> >>>>>>>>>>>>>>> 
> >>>>>>>>>>>>>>> Hi Peter,
> >>>>>>>>>>>>>>> You are welcome to add  an appropriate handler.
> >>>>>>>>>>>>>> 
> >>>>>>>>>>>>>> I think Vadim refers to this HV MSR
> >>>>>>>>>>>>>> http://msdn.microsoft.com/en-us/library/windows/hardware/ff5
> >>>>>>>>>>>>>> 42 633%28 v=vs .85 %29.aspx
> >>>>>>>>>>>>> 
> >>>>>>>>>>>>> This one is pretty simple to support. Please see attachments
> >>>>>>>>>>>>> for more details. I was thinking about synthetic  timers
> >>>>>>>>>>>>> http://msdn.microsoft.com/en-
> >>>>>>>>>>>>> us/library/windows/hardware/ff542758(v=vs.85).aspx
> >>>>>>>>>>>> 
> >>>>>>>>>>>> is this what microsoft qpc uses as clocksource in hyper-v?
> >>>>>>>>>>> 
> >>>>>>>>>>> Yes, it should be enough for Win7 / W2K8R2.
> >>>>>>>>>> 
> >>>>>>>>>> To clarify the thing that microsoft qpc uses is what is
> >>>>>>>>>> implemented by the patch Vadim attached to his previous email.
> >>>>>>>>>> But I believe that additional qemu patch is needed for Windows
> >>>>>>>>>> to actually use it.
> >>>>>>>>> 
> >>>>>>>>> You are right.
> >>>>>>>>> bits 1 and 9 must be set to on in leaf 0x40000003 and HPET
> >>>>>>>>> should be completely removed from ACPI.
> >>>>>>>> 
> >>>>>>>> could you advise how to do this and/or make a patch?
> >>>>>>>> 
> >>>>>>>> the stuff you send yesterday is for qemu, right? would
> >>>>>>>> it be possible to use it in qemu-kvm also?
> >>>>>>> 
> >>>>>>> No, they are for kernel.
> >>>>>> 
> >>>>>> i meant the qemu.diff file.
> >>>>> 
> >>>>> Yes, I missed the second attachment.
> >>>>> 
> >>>>>> if i understand correctly i have to pass -cpu host,+hv_refcnt to
> >>>>>> qemu?
> >>>>> 
> >>>>> Looks like it.
> >>>> 
> >>>> ok, so it would be interesting if it helps to avoid the pmtimer reads
> >>>> we observed earlier. right?
> >>> 
> >>> Yes.
> >> 
> >> first feedback: performance seems to be amazing. i cannot confirm that
> >> it breaks hv_spinlocks, hv_vapic and hv_relaxed.
> >> why did you assume this?
> > 
> > I didn't mean that hv_refcnt will break any other hyper-v features.
> > I just want to say that turning hv_refcnt on (as any other hv_ option)
> > will crash Win8 on boot-up.
> 
> yes, i got it meanwhile ;-)
> 
> let me know what you think should be done to further test
> the refcnt implementation.
> 
> i would suggest to return at least 0xFFFFFFFF if msr 0x40000021
> is read.
IIRC Win7(W2k8R2) only reads this MSR. Win8 reads and writes.
> 
> peter
> 
> > Cheers,
> > Vadim.
> > 
> >> no more pmtimer reads. i can now almost fully utililizy a 1GBit
> >> interface with a file transfer while there was not one
> >> cpu core fully utilized as observed with pmtimer. some live migration
> >> tests revealed that it did not crash even under load.
> >> 
> >> @vadim: i think we need a proper patch for the others to test this ;-)
> >> 
> >> what i observed: is it right, that HV_X64_MSR_TIME_REF_COUNT is missing
> >> in msrs_to_save[] in x86/x86.c of the kernel module?
> >> 
> >> thanks for you help,
> >> peter
> >> 
> >>> --
> >>> 
> >>> 			Gleb.